1. Field of the Invention
The present invention relates to a video signal compression-encoding apparatus, a recording medium, and a video signal reproducing apparatus.
2. Description of the Related Art
In recent years, a process for compression-encoding a video signal has been studied along with the advancement of digital storage media. In International Organization for Standardization (ISO), standardization efforts of a method for compression-encoding moving images have been made in Moving Picture Image Coding Experts Group (MPEG) of International Electrotechnical Commission (IEC).
Digitized moving image data contains a great amount of information. Therefore, the digitized moving image data is compression-encoded to a degree that information is not noticeably degraded in an original image.
According to a compression-encoding method, several frames or several fields are placed in one group, and at least one frame or one field is subjected to intra-frame or intra-field compression-encoding processing at a relatively low compression rate and the remaining frames or fields are subjected to inter-frame or inter-field compression-encoding processing at a relatively high compression rate.
The above-mentioned combination of the intra-frame or intra-field compression-encoding processing and the inter-frame or inter-field compression-encoding processing can relatively suppress degradation of an image quality while improving a compression rate. By being subjected to compression-encoding processing, image data can be recorded in and reproduced from a recording medium for a longer period of time.
However, according to the above-mentioned conventional method, an I-frame appears at predetermined intervals (e.g., at intervals of 15 frames). Therefore, the entry point of a scene is found on a group of picture (hereinafter, referred to as a "GOP") basis, but not on a frame basis. This configuration also makes it impossible to place a frame after the change of a scene at a leading edge of a GOP, causing quality degradation of an image decoded and reproduced from a recording medium.